X-Y stages are well known; they are typically used in machine tools and other applications where two dimensional precise movement is needed to position an object supported on the stage. An application of X-Y stages is in lithography equipment e.g. for semiconductor wafer processing. In this case, a stage is typically used in a lithography tool to position, in two dimensions, the reticle (mask). A separate stage is sometimes provided to position the semiconductor wafer or other workpiece. Mechanical and thermal disturbances are problematic since they reduce the resolution, positioning accuracy and useful positioning speed of the stage and the lithography process. Hence there is a need for improved stages. Increasingly there is also a need for stages which can operate in a vacuum, e.g. for use in electron beam lithography.